This invention concerns arthroplasty, and, more particularly, resides in improved cutting guides having features to better assist a surgeon in preparing a bone, for example, to receive an implant.
Whether for primary or revision arthroplasty, cutting guides are typically employed to ensure that the bone saw performs resections corresponding to mating surfaces of the prosthetic component. For example, in a femoral knee replacement, cutting guides or blocks are temporarily secured to the distal end of the femoral shaft, and include slots into which the blade of an oscillating saw is inserted to shape the end of the bone in accordance with corresponding surfaces of-the prosthetic element.
In the case of a revision, the procedure is usually more elaborate due to deterioration of the previously prepared surfaces resulting from decomposition of the bone/prosthesis interface, necrosis, and other factors. Cutting blocks are also typically used in revision procedures, though bone deficiency often renders stabilization of the block impossible. In addition, if the cutting block includes a stem, the positioning of the stemmed implant can alter the fit of the final prothesis relative to the bone. More recently introduced techniques attempt to base the cuts on an intramedullary guide to which additional cutting blocks are mounted. Though such approaches improve bone cutting accuracy, there remains an unacceptable margin of error, the correction of which in some cases requiring a freehand shaping of the bone.
The present invention accordingly provides improved cutting guides which enable one performing a resection to better predict and execute required cut characteristics. Broadly, at least a portion of the body comprising the cutting guide is transparent, thereby enabling the practitioner to better estimate cut depth and/or visualize the resection as it is being performed. Preferably one or more slots are used to guide a cutting saw, with the volume of the body surrounding the slots being transparent.
In one embodiment, at least a portion of the outer surface of the body is further shaped to interact with another bone or prosthetic element as part of a joint, thereby enabling the device to function both as a trial and as a cutting guide. For example, if adapted for use in femoral knee arthroplasty, the outer shape of the body may include condylar protrusions which cooperate with corresponding tibial surfaces or prosthetic inserts. In this combination trial/cutting-guide embodiment the device may likewise advantageously be at least partially transparent to assist in estimating cut orientation or depth, and to visualize a particular resection in progress. Although primarily intended for use in conjunction with preparing a bone surface to receive a prosthetic component, the invention is applicable to any bone-cutting procedure which might benefit from improved accuracy.